Hi all,

I have a question about PDL::IO::FITS and in particular the methods hdr & 
gethdr.

I've got a Moose script that works fine with PDL::IO::FITS and adds fine the 
usual FITS fields to a FITS 
header. The resulting FITS file is read fine by SAOImage and the FITS fields 
are in the order I want.

The problem is with fields that are potential duplicates such as COMMENT and 
HISTORY.

I noticed that PDL::IO::FITS doesn't make use of Tie::DxHash which specifically 
handles duplicate keys in tied hashes. Nor does Astro::FITS::Header.

I also don't see exported in PDL::IO::FITS the methods insert or index from 
Astro::FITS::Header which might be the right methods to call for adding COMMENT 
fields.

When I create a tied hash using Tie::DxHash and copy over the data returned by 
gethdr, I get a tied hash with duplicate COMMENT fields in the order I want.

I then save the resultant updated FITS header hash using sethdr.

But when I view the FITS file in SAOImage for example I see the added fields in 
alphabetical order, not the tied order they were saved in. I also don't see any 
COMMENT fields.

If I don't use Tie::DxHash, but just add the COMMENT field directly to the tied 
hash returned by gethdr, I get only 1 COMMENT field in the header, with the 
last value assigned to it, which makes sense since Tie::DxHash isn't being 
used. Hence no duplicate keys allowed.

What is the recommended way to add multiple COMMENT fields using PDL::IO::FITS ?

Thanks, 

--Ed




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